Waste Plastics to Fuel

More and more cities are banning single-use plastic grocery bags
because they are hard to recycle and represent a large volume of
slow-to-decompose landfill waste as well as contribute to a considerable
amount of pollution. In fact, as of 2008, all plastics counted together
made up approximately 12% of municipal solid waste in the United
States. But what that plastic waste could be recovered and turned into
something useful? ISTC researchers B.K. Sharma and Kishore Rajagopalan
collaborated with the United States Department of Agriculture (USDA) to
convert plastic bags into fuel.

The team collected high-density polyethylene (HDPE) bags from local
retailers and fed them into a pyrolysis unit to yield plastic crude
oil (PCO). They then distilled the PCO,
giving rise to gasoline and two types of diesel. These were analyzed
and compared against conventional petroleum-derived diesel fuel
standards. After adding antioxidants to their products, they fell within
nearly all specifications of the conventional diesel standards. In
fact, the team’s HDPE-derived
fuels were superior to conventional petroleum diesel in terms of
lubricity and derived cetane number, which relates to the fuel’s
ignition quality. The researchers concluded that plastic-derived diesel
can be safely and efficiently blended into petroleum diesel fuel,
while minimizing landfill waste. This research was funded in part as a
seed grant from the Illinois Hazardous Waste Research Fund.

After successfully converting plastic bags to fuel, Sharma and
Rajagopalan went a step further to look at converting low-value plastics
into gasoline and diesel. While the best options for plastic are
reducing production, reusing, and recycling, some plastics are made (for
a variety of reasons) that cannot be recycled and are destined for
landfill. These plastics are called low-value plastics, and in those
cases, the better alternative would be to make fuel from the plastic
instead of having it end up in landfill. Often low-value plastics are
made of several plastic polymers which have different melting and
thermal depolymerization temperatures. Therefore, Sharma and Rajagopalan
are working on optimizing the pyrolysis and depolymerization process
for these types of plastics in order to produce an alternative fuel
source. Results are expected in Spring 2016.